1 Buffer Systems

2 Introduction Regulation of hydrogen ion Buffer systemAcid-base regulation Regulation of hydrogen ion Buffer system Respiratory regulation Renal regulation

3 Why To Regulate To maintain homeostasis Regulates enzymatic functions

4 Acids And Bases Release protons (H) ;Eg-H2CO3 , HCLAccept protons (H) ; Eg-HCO3

5 Types of acids and basesStrong acids Release large amount of Hydrogen ions Weak acids Release small amount of Hydrogen ions Strong bases Accept large amount of Hydrogen ions Weak bases Accept small amount of Hydrogen ions

6 Hydrogen ion conc. Determines pH

7 What Is Buffer ??? A buffer is a solution (or a substance) that has the ability to maintain pH and bring it back to its optimal value by addition or removal of hydrogen ions Buffer + H H buffer

8 In this way hydrogen ion concentration is maintainedContd…. When Hydrogen ion conc. Increases Reaction shifts towards right When Hydrogen ion conc. Decreases Reaction shifts towards left In this way hydrogen ion concentration is maintained

9 Types of chemical bufferCarbonic acid-bicarbonate – Buffering changes caused by organic and fixed acids Protein buffer system-Amino acids Minor buffering system- Phosphate –Buffer pH in the ICF

10 Figure 27.7

11 Carbonic Acid-Bicarbonate Buffering SystemCarbonic acid-bicarbonate buffer system Weak acid – H2CO3 Bicarbonate salt (NaHCO3) Strong acid is added When HCL is added Hydrogen conc increases CO2 + H2O  H2CO3  H + HCO3

12 Contd… H+ conc. Reduces In this way CO2 conc. decreasesStrong base is added H+ conc. Reduces NaOH + H2CO NaHCO3+H2O In this way CO2 conc. decreases This inhibits respiration.

13

14 Bicarbonate buffer- Has the following limitations: Cannot protect the ECF from pH changes due to increased or depressed CO2 levels Only functions when respiratory system and control centers are working normally It is limited by availability of bicarbonate ions (bicarbonate reserve).

15 Phosphate buffer system-Main elements of phosphate buffer system- - H2PO4, and HPO4 Phosphoric acid changes pretty quickly into dihydrogen phosphate, or H2PO4-.   This dihydrogen phosphate is an efficient buffer.

16 Contd…

17 Contd…. Phosphate buffer system in the ECF is low compared to the bicarbonate buffer. Its buffering power is less compared to the bicarbonate buffer. It has its importance in the renal tubules of kidneys for two reasons. .

18 Contd 1.Conc. of phosphate is more in tubules.2. Tubular fluid has lower pH. Conc. of phosphate is more in ICF compared to ECF.

19 Protein buffer system Proteins are made up of amino acidsAmino acids have a central carbon with four groups off of it: 1.a carboxyl group (COOH) 2.an amino group (NH2) 3.a hydrogen atom 4.an R group .  

20 Structure of amino acids

21 Contd… The carboxyl and amino groups are what enable proteins to act as buffers. Carboxyl group is attached to the amino acid central carbon:   C - COOH Carboxyl group consists of a double bond to one of the oxygens and a single bond to the hydroxyl group. 

22 Contd... At neutral pH the carboxyl ion is present as COO instead of COOH. Acidic medium – becomes COOH Basic medium – becomes COO.

23 Contd… Acidic medium – becomes NH3+Amino group is attached to the amino acid central carbon:  C - NH2. Neutral pH, the amino group is actually NH3+ rather than just NH2. Acidic medium – becomes NH3+ Basic medium- becomes NH2

24 Contd..

25 Respiratory regulationWhen alveolar ventilation increases CO2 conc. In ECF decreases H+ conc. decreases Or vice versa

26 Respiratory regulation Contd…Pulmonary expiration of CO2 balances metabolic formation of CO2 1.2 mol/L of dissolved CO2 is present in the ECF corresponding to pCO2 of 40 mm/hg Rate of pulmonary ventilation is inversely proportional to CO2 & pCO2 So either pulmonary ventilation rate of CO2 or its formation by tissues can change pCO2 in ECF.

27 Contd… If alveolar ventilation increases the pCO2 decreases.Increasing alveolar ventilation decreases ECF hydrogen ion conc. And raises pH If alveolar ventilation increases the pCO2 decreases. If alveolar ventilation decreases the pCO2 increases. Twice rise of AV--rises pH of ECF by about 0.23 Decrease of AV to ¼ -- decreases pH by 0.45

28 Contd… Increased Hydrogen ion conc. Stimulates alveolar ventilationChange in alveolar ventilation rate is much greater in reduced levels of pH than in increased levels of pH

29 Reason Alveolar ventilation rate decreases Increases pH O2 added in blood reduces Demand of O2 in blood increases pO2 also decreases Stimulates ventilation

30 Feedback control of Hydrogen ion conc. By RSH conc. Falls below normal Respiration is depressed Alveolar ventilation decreases H increases back to normal

31 Bufffering power of RS The kidneys work in elimination of hydrogen ion conc. and control imbalance. Its capacity is 1-2 times as much as other chemical buffers.

32 Impairment of lungs function:Impairment of lung function leads to emphysema and respiratory disorders. Kidneys play a major physiologic mechanism for returning pH to normal

33 Renal mechanism of acid-base regulationKidneys regulate the blood pH by 1. maintaining alkali reserves 2. excreting / reabsorbing acid/base. Urine pH is lower than blood pH Kidneys- Acidification of urine.

34 Contd… Excretion of hydrogen ions Reabsorption of bicarbonate ionExcretion of ammonium ions

35 Disorders of acid-base regulation cont…Respiratory acidosis Respiratory alkalosis Metabolic acidosis Metabolic alkalosis

36 Contd… Respiratory acid-base disorders are initiated by an increase or decrease in partial pressure of carbondioxide whereas metabolic disorders are initiated by an increase or decrease in bicarbonate ion.

37 Contd… Alkalosis - Partial pressure of oxygen increases.Acidosis – Partial pressure of carbondioxide increases.

38 Contd… Respiratory acidosis-Decrease in rate of pulmonary ventilation- Increased pCO2 of ECF. Respiratory alkalosis- Increased rate of ventilation- Decrease the pCO2

39 Respiratory acidosis Figure 27.12a

40 Respiratory alkalosisFigure 27.12b

41 Contd… Metabolic acidosis- Decreased ECF bicarbonate ion conc.Metabolic alkalosis- Increased ECF bicarbonate ion conc.

42 Contd… DISTURBANCE pH PRIMARY CHANGE RATIO SECONDARYMetabolic Acidosis Decreased Deficit of bi- carbonate <20 Decrease in PaCO2 Metabolic Alkalosis Increased Excess of bicarbonate >20 Increase in PaCO2 Respiratory acidosis Excess of carbonic acid Increase in bicarbonate alkalosis Deficit of carbonic acid Decrease in bicarbonate

43 Contd… Causes - Metabolic acidosis 1. Renal tubular acidosis2. Diarrhea 3. Vomiting of intestinal contents 4. Diabetes Mellitus 5. Ingestion of acids 6. Chronic renal failure

44 Contd… Causes- Metabolic alkalosis 1. Vomiting of gastric contents2. Ingestion of alkaline drugs etc.

45 Correction by renal for…Acidosis- Increased excretion of hydrogen ions and addition of bicarbonate ions to the ECF. Alkalosis- Decreased tubular secretion of hydrogen ions and increased excretion of HCO3_

46 The Central Role of the Carbonic Acid-Bicarbonate Buffer System in the Regulation of Plasma pHFigure 27.11a

47 The Central Role of the Carbonic Acid-Bicarbonate Buffer System in the Regulation of Plasma pHFigure 27.11b

48 Acid-Base Disorders Respiratory acid base disordersResult when abnormal respiratory function causes rise or fall in CO2 in ECF Metabolic acid-base disorders Generation of organic or fixed acids Anything affecting concentration of bicarbonate ions in ECF

49 Respiratory acidosis Results from excessive levels of CO2 in body fluids

50 Respiratory alkalosisRelatively rare condition Associated with hyperventilation

51 Metabolic acidosis Major causes are: Depletion of bicarbonate reserveInability to excrete hydrogen ions at kidneys Production of large numbers of fixed / organic acids Bicarbonate loss due to chronic diarrhea

52 Figure The Response to Metabolic Acidosis

53 Figure Metabolic Alkalosis